The determination of the surface stress state and/or the microstructure state is an important task when monitoring the stress on mechanical workpieces. Various measuring methods exist for this purpose. One of the most frequently used methods operates with strain gauges which have to be applied to the surface at the measuring point for this purpose using a complicated method. In the case of moving workpieces, a telemetry system for active supply and transmission of measured values is additionally required. Furthermore, contactlessly operating optical methods are also known. However, both are very complicated.